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© Martina Haller, Andreas K Hock, Evangelos Giampazolias, Andrew Oberst, Douglas R Green, Jayanta Debnath, Kevin M Ryan, Karen H Vousden, and Stephen W G Tait.During macroautophagy, conjugation of ATG12 to ATG5 is essential for LC3 lipidation and autophago

Canonical RAS signaling, including PI3K/AKT- and RAF/MEK-dependent activities, results mainly from RAS•GTP interaction with its effectors at the plasma membrane. Here, we identified a fundamental, oncogenic, noncanonical RAS•GTP activity that increases XPO1-dependent export of nuclear protein cargo into the cytoplasm and is independent of PI3K/AKT and RAF/MEK signaling. This RAS-dependent step acts downstream from XPO1 binding to nuclear protein cargo and is mediated by a perinuclear protein complex between RAS•GTP and RanGAP1 that facilitates hydrolysis of Ran•GTP to Ran•GDP, which promotes release of nuclear protein cargo into the cytoplasm. The export of nuclear EZH2, which promotes cytoplasmic degradation of the DLC1 tumor suppressor protein, is a biologically important component of this pro-oncogenic activity. Conversely, preventing nuclear protein export contributes to the antitumor activity of KRAS inhibition, which can be further augmented by reactivating the tumor suppressor activity of DLC1 or potentially combining RAS inhibitors with other cancer treatments., Competing Interests: Competing interests All authors declare no competing interests., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

White adipose tissue (WAT) is crucial for whole-body energy homeostasis and plays an important role in metabolic and hormonal regulation. While healthy WAT undergoes controlled expansion and contraction to meet the body's requirements, dysfunctional WAT in conditions like obesity is characterized by excessive tissue expansion, alterations in lipid homeostasis, inflammation, hypoxia, and fibrosis. Obesity is strongly associated with an increased risk of numerous cancers, with obesity-induced WAT dysfunction influencing cancer development through various mechanisms involving both systemic and local interactions between adipose tissue and tumors. Unhealthy obese WAT affects circulating levels of free fatty acids and factors like leptin, adiponectin, and insulin, altering systemic lipid metabolism and inducing inflammation that supports tumor growth. Similar mechanisms are observed locally in an adipose-rich tumor microenvironment (TME), where WAT cells can also trigger extracellular matrix remodeling, thereby enhancing the TME's ability to promote tumor growth. Moreover, tumors reciprocally interact with WAT, creating a bidirectional communication that further enhances tumorigenesis. This review focuses on the complex interplay between obesity, WAT dysfunction, and primary tumor growth, highlighting potential targets for therapeutic intervention., (© 2024 The Author(s). The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Fueled by technological and conceptual advancements over the past two decades, research in cancer metabolism has begun to answer questions dating back to the time of Otto Warburg. But, as with most fields, new discoveries lead to new questions. This review outlines the emerging challenges that we predict will drive the next few decades of cancer metabolism research. These include developing a more realistic understanding of how metabolic activities are compartmentalized within cells, tissues, and organs; how metabolic preferences in tumors evolve during cancer progression from nascent, premalignant lesions to advanced, metastatic disease; and, most importantly, how we can best translate basic observations from preclinical models into novel therapies that benefit patients with cancer. With modern tools and an incredible amount of talent focusing on these problems, the upcoming decades should bring transformative discoveries., (Copyright © 2024 Cold Spring Harbor Laboratory Press; all rights reserved.)

The phenomenon of mixed/heterogenous treatment responses to cancer therapies within an individual patient presents a challenging clinical scenario. Furthermore, the molecular basis of mixed intra-patient tumor responses remains unclear. Here, we show that patients with metastatic lung adenocarcinoma harbouring co-mutations of EGFR and TP53, are more likely to have mixed intra-patient tumor responses to EGFR tyrosine kinase inhibition (TKI), compared to those with an EGFR mutation alone. The combined presence of whole genome doubling (WGD) and TP53 co-mutations leads to increased genome instability and genomic copy number aberrations in genes implicated in EGFR TKI resistance. Using mouse models and an in vitro isogenic p53-mutant model system, we provide evidence that WGD provides diverse routes to drug resistance by increasing the probability of acquiring copy-number gains or losses relative to non-WGD cells. These data provide a molecular basis for mixed tumor responses to targeted therapy, within an individual patient, with implications for therapeutic strategies., (© 2024. The Author(s).)

Metabolic changes contribute to cancer initiation and progression through effects on cancer cells, the tumor microenvironment and whole-body metabolism. Alterations in serine metabolism and the control of one-carbon cycles have emerged as critical for the development of many tumor types. In this Review, we focus on the mitochondrial folate cycle. We discuss recent evidence that, in addition to supporting nucleotide synthesis, mitochondrial folate metabolism also contributes to metastasis through support of antioxidant defense, mitochondrial protein synthesis and the overflow of excess formate. These observations offer potential therapeutic opportunities, including the modulation of formate metabolism through dietary interventions and the use of circulating folate cycle metabolites as biomarkers for cancer detection., (© 2024. Springer Nature America, Inc.)

The last 50 years have witnessed extraordinary developments in understanding mechanisms of carcinogenesis, synthesized as the hallmarks of cancer. Despite this logical framework, our understanding of the molecular basis of systemic manifestations and the underlying causes of cancer-related death remains incomplete. Looking forward, elucidating how tumors interact with distant organs and how multifaceted environmental and physiological parameters impinge on tumors and their hosts will be crucial for advances in preventing and more effectively treating human cancers. In this perspective, we discuss complexities of cancer as a systemic disease, including tumor initiation and promotion, tumor micro- and immune macro-environments, aging, metabolism and obesity, cancer cachexia, circadian rhythms, nervous system interactions, tumor-related thrombosis, and the microbiome. Model systems incorporating human genetic variation will be essential to decipher the mechanistic basis of these phenomena and unravel gene-environment interactions, providing a modern synthesis of molecular oncology that is primed to prevent cancers and improve patient quality of life and cancer outcomes., Competing Interests: Declaration of interests C.A. reports employment at Saga Diagnostics and reports options to own stock in the company. C.A. and C.S. are listed as inventors on a European patent application relating to assay technology to detect tumor recurrence (PCT/GB2017/053289). This patent has been licensed to commercial entities and, under their terms of employment, C.A. and C.S. are due a revenue share of any revenue generated from such license(s). C.A. and C.S. declare a patent application (PCT/US2017/028013) for methods to detect lung cancer. C.A. and C.S. are named inventors on a patent application to determine methods and systems for tumor monitoring (PCT/EP2022/077987). C.A. and C.S. are named inventors on a provisional patent protection related to a ctDNA detection algorithm. J.A.J. has received honoraria for speaking at research symposia organized by Bristol Meyers Squibb and Glenmark Pharmaceuticals and previously served on the SAB of Pionyr Immunotherapeutics. D.H. is a founder and member of the BoD and SAB of Opna Bio, and a member of the SABs of Pfizer, Cellestia Biotech, 4D Molecular Therapeutics, and AtG Therapeutics. F.A. reports travel/accommodation/expenses from AstraZeneca, GlaxoSmithKline, Novartis, Pfizer, and Roche, and his institution has received research funding from AstraZeneca, Daiichi Sankyo, Lilly, Novartis, Pfizer, and Roche. C.M. Consultant/Advisory fees from Amgen, Astellas, AstraZeneca, Bayer, BeiGene, BMS, Celgene, Debiopharm, Genentech, Ipsen, Janssen, Lilly, MedImmune, MSD, Novartis, Pfizer, Roche, Sanofi, Orion. Principal/sub-Investigator of Clinical Trials for AbbVie, Aduro, Agios, Amgen, Argen-x, Astex, AstraZeneca, Aveo pharmaceuticals, Bayer, Beigene, Blueprint, BMS, Boeringer Ingelheim, Celgene, Chugai, Clovis, Daiichi Sankyo, Debiopharm, Eisai, Eos, Exelixis, Forma, Gamamabs, Genentech, Gortec, GSK, H3 biomedecine, Incyte, InnatePharma, Janssen, Kura Oncology, Kyowa, Lilly, Loxo, Lysarc, Lytix Biopharma, Medimmune, Menarini, Merus, MSD, Nanobiotix, Nektar Therapeutics, Novartis, Octimet, Oncoethix, Oncopeptides AB, Orion, Pfizer, Pharmamar, Pierre Fabre, Roche, Sanofi, Servier, Sierra Oncology, Taiho, Takeda, Tesaro, and Xencor. R.B. is founder of Oncosence. M.A.F. is founder and shareholder of Celesta Therapeutics. A.H. is a paid consultant for Calida Therapeutics. M.J.-H. has consulted for, and is a member of, the Achilles Therapeutics Scientific Advisory Board and Steering Committee, has received speaker honoraria from Pfizer, Astex Pharmaceuticals, Oslo Cancer Cluster, Bristol Myers Squibb, and is listed as a co-inventor on a European patent application relating to methods to detect lung cancer PCT/US2017/028013), this patent has been licensed to commercial entities and, under terms of employment, M.J.-H. is due a share of any revenue generated from such license(s). J.W.L. advises Restoration Foodworks, Nanocare Technologies, and Cornerstone Pharmaceuticals. S.L. received research funding to institution from Novartis, Bristol Myers Squibb, MSD, Puma Biotechnology, Eli Lilly, Nektar Therapeutics, AstraZeneca/Daiichi Sankyo, and Seattle Genetics. S.L. has acted as consultant (not compensated) to Seattle Genetics, Novartis, Bristol Myers Squibb, MSD, AstraZeneca/Daiichi Sankyo, Eli Lilly, Pfizer, Gilead Therapeutics, Nektar Therapeutics, PUMA Biotechnologies and Roche-Genentech. S.L. has acted as consultant (paid to institution) to Novartis, GlaxoSmithKline, Roche-Genentech, AstraZeneca/Daiichi Sankyo, Pfizer, Gilead Therapeutics, Seattle Genetics, MSD, Tallac Therapeutics, Eli Lilly, and Bristol Myers Squibb. I.M. is a consultant of LIfT BioSciences. K.M. has received honoraria from LEO Pharma, Pfizer and Bayer PLC. She has received research funding from LEO Pharma and Bayer PLC. S.Q. is a founder, CSO, and holds stock options in Achilles Therapeutics. C.S. acknowledges grants from AstraZeneca, Boehringer Ingelheim, Bristol Myers Squibb, Pfizer, Roche-Ventana, Invitae (previously Archer Dx Inc—collaboration in minimal residual disease sequencing technologies), Ono Pharmaceutical, and Personalis. He is Chief Investigator for the AZ MeRmaiD 1 and 2 clinical trials and is the Steering Committee Chair. He is also Co-Chief Investigator of the NHS Galleri trial funded by GRAIL and a paid member of GRAIL’s Scientific Advisory Board. He receives consultant fees from Achilles Therapeutics (also SAB member), Bicycle Therapeutics (also a SAB member), Genentech, Medicxi, China Innovation Centre of Roche (CICoR) formerly Roche Innovation Centre—Shanghai, Metabomed (until July 2022), Relay Therapeutics, and the Sarah Cannon Research Institute. C.S. has received honoraria from Amgen, AstraZeneca, Bristol Myers Squibb, GlaxoSmithKline, Illumina, MSD, Novartis, Pfizer, and Roche-Ventana. C.S. has previously held stock options in Apogen Biotechnologies and GRAIL, and currently has stock options in Epic Bioscience, Bicycle Therapeutics, and has stock options and is co-founder of Achilles Therapeutics. Patents: C.S. declares a patent application (PCT/US2017/028013) for methods to lung cancer); targeting neoantigens (PCT/EP2016/059401); identifying patent response to immune checkpoint blockade (PCT/EP2016/071471), determining HLA LOH (PCT/GB2018/052004); predicting survival rates of patients with cancer (PCT/GB2020/050221); identifying patients who respond to cancer treatment (PCT/GB2018/051912); methods for lung cancer detection (US20190106751A1). C.S. is an inventor on a European patent application (PCT/GB2017/053289) relating to assay technology to detect tumor recurrence. This patent has been licensed to a commercial entity and under their terms of employment C.S. is due a revenue share of any revenue generated from such license(s). K.H.V. is on the board of directors and shareholder of Bristol Myers Squibb and on the science advisory board (with stock options) of PMV Pharma, RAZE Therapeutics, Volastra Pharmaceuticals and Kovina Therapeutics. She is on the SAB of Ludwig Cancer and a co-founder and consultant of Faeth Therapeutics. She has been in receipt of research funding from Astex Pharmaceuticals and AstraZeneca and contributed to CRUK Cancer Research Technology filing of patent application WO/2017/144877. J.W. is an inventor on a US patent application (PCT/US17/53.717) submitted by the University of Texas MD Anderson Cancer Center which covers methods to enhance immune checkpoint blockade responses by modulating the microbiome, reports compensation for speaker’s bureau and honoraria from Imedex, Dava Oncology, Omniprex, Illumina, Gilead, PeerView, Physician Education Resource, MedImmune, Exelixis and Bristol Myers Squibb, and has served as a consultant/advisory board member for Roche/Genentech, Novartis, AstraZeneca, GlaxoSmithKline, Bristol Myers Squibb, Micronoma, OSE therapeutics, Merck, and Everimmune. Dr. Wargo receives stock options from Micronoma and OSE therapeutics. A.W. is on the board of Regain Therapeutics., (Copyright © 2024. Published by Elsevier Inc.)

For our special issue on stress, we asked scientists about recovering from the stress of the pandemic, including some who shared insights with us in mid-2020. They discuss the importance of teamwork, reassessing priorities, and the added stresses of the cost-of-living crisis, funding cuts, and retaining scientists in academia., Competing Interests: Declaration of interests B.A.S. is a member of the scientific advisory board of Biotheryx and is a co-inventor of intellectual property related to DCN1 inhibitors licensed to Cinsano. K.H.V. is a member of the Molecular Cell Advisory Board and is funded by and an advisor for Cancer Research UK., (Copyright © 2023 Elsevier Inc. All rights reserved.)

In this study, the impact of the apolipoprotein B mRNA-editing catalytic subunit-like (APOBEC) enzyme APOBEC3B (A3B) on epidermal growth factor receptor (EGFR)-driven lung cancer was assessed. A3B expression in EGFR mutant (EGFRmut) non-small-cell lung cancer (NSCLC) mouse models constrained tumorigenesis, while A3B expression in tumors treated with EGFR-targeted cancer therapy was associated with treatment resistance. Analyses of human NSCLC models treated with EGFR-targeted therapy showed upregulation of A3B and revealed therapy-induced activation of nuclear factor kappa B (NF-κB) as an inducer of A3B expression. Significantly reduced viability was observed with A3B deficiency, and A3B was required for the enrichment of APOBEC mutation signatures, in targeted therapy-treated human NSCLC preclinical models. Upregulation of A3B was confirmed in patients with NSCLC treated with EGFR-targeted therapy. This study uncovers the multifaceted roles of A3B in NSCLC and identifies A3B as a potential target for more durable responses to targeted cancer therapy., (© 2023. The Author(s).)

Serine is a vital amino acid in tumorigenesis. While cells can perform de novo serine synthesis, most transformed cells rely on serine uptake to meet their increased biosynthetic requirements. Solute carriers (SLCs), a family of transmembrane nutrient transport proteins, are the gatekeepers of amino acid acquisition and exchange in mammalian cells and are emerging as anticancer therapeutic targets; however, the SLCs that mediate serine transport in cancer cells remain unknown. Here we perform an arrayed RNAi screen of SLC-encoding genes while monitoring amino acid consumption and cell proliferation in colorectal cancer cells using metabolomics and high-throughput imaging. We identify SLC6A14 and SLC25A15 as major cytoplasmic and mitochondrial serine transporters, respectively. We also observe that SLC12A4 facilitates serine uptake. Dual targeting of SLC6A14 and either SLC25A15 or SLC12A4 diminishes serine uptake and growth of colorectal cancer cells in vitro and in vivo, particularly in cells with compromised de novo serine biosynthesis. Our results provide insight into the mechanisms that contribute to serine uptake and intracellular handling., (© 2023. The Author(s).)

Previous studies have revealed a role for proline metabolism in supporting cancer development and metastasis. In this study, we show that many cancer cells respond to loss of attachment by accumulating and secreting proline. Detached cells display reduced proliferation accompanied by a general decrease in overall protein production and de novo amino acid synthesis compared to attached cells. However, proline synthesis was maintained under detached conditions. Furthermore, while overall proline incorporation into proteins was lower in detached cells compared to other amino acids, there was an increased production of the proline-rich protein collagen. The increased excretion of proline from detached cells was also shown to be used by macrophages, an abundant and important component of the tumor microenvironment. Our study suggests that detachment induced accumulation and secretion of proline may contribute to tumor progression by supporting increased production of extracellular matrix and providing proline to surrounding stromal cells.

Augmented T cell function leading to host damage in autoimmunity is supported by metabolic dysregulation, making targeting immunometabolism an attractive therapeutic avenue. Canagliflozin, a type 2 diabetes drug, is a sodium glucose co-transporter 2 (SGLT2) inhibitor with known off-target effects on glutamate dehydrogenase and complex I. However, the effects of SGLT2 inhibitors on human T cell function have not been extensively explored. Here, we show that canagliflozin-treated T cells are compromised in their ability to activate, proliferate, and initiate effector functions. Canagliflozin inhibits T cell receptor signaling, impacting on ERK and mTORC1 activity, concomitantly associated with reduced c-Myc. Compromised c-Myc levels were encapsulated by a failure to engage translational machinery resulting in impaired metabolic protein and solute carrier production among others. Importantly, canagliflozin-treated T cells derived from patients with autoimmune disorders impaired their effector function. Taken together, our work highlights a potential therapeutic avenue for repurposing canagliflozin as an intervention for T cell-mediated autoimmunity., Competing Interests: Declaration of interests K.H.V. is on the board of directors and shareholder of Bristol Myers Squibb, a shareholder of GRAIL, and on the science advisory board of PMV Pharma, RAZE Therapeutics, Volastra Pharmaceuticals, and Ludwig Cancer. She is a co-founder and consultant of Faeth Therapeutics, funded by Khosla Ventures. She has been in receipt of research funding from Astex Pharmaceuticals and AstraZeneca and contributed to CRUK Cancer Research Technology filing of patent application WO/2017/144877., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Mitochondrial 10-formyltetrahydrofolate (10-formyl-THF) is utilized by three mitochondrial enzymes to produce formate for nucleotide synthesis, NADPH for antioxidant defense, and formyl-methionine (fMet) to initiate mitochondrial mRNA translation. One of these enzymes-aldehyde dehydrogenase 1 family member 2 (ALDH1L2)-produces NADPH by catabolizing 10-formyl-THF into CO 2 and THF. Using breast cancer cell lines, we show that reduction of ALDH1L2 expression increases ROS levels and the production of both formate and fMet. Both depletion of ALDH1L2 and direct exposure to formate result in enhanced cancer cell migration that is dependent on the expression of the formyl-peptide receptor (FPR). In various tumor models, increased ALDH1L2 expression lowers formate and fMet accumulation and limits metastatic capacity, while human breast cancer samples show a consistent reduction of ALDH1L2 expression in metastases. Together, our data suggest that loss of ALDH1L2 can support metastatic progression by promoting formate and fMet production, resulting in enhanced FPR-dependent signaling., Competing Interests: Declaration of interests K.H.V. is on the board of directors and is a shareholder of Bristol Myers Squibb and is on the scientific advisory board (with stock options) of PMV Pharma, RAZE Therapeutics, Volastra Pharmaceuticals, and Kovina Therapeutics. She is on the scientific advisory board (SAB) of Ludwig Cancer and is a co-founder and consultant of Faeth Therapeutics. She has been in receipt of research funding from Astex Pharmaceuticals and AstraZeneca and contributed to the CRUK Cancer Research Technology filing of patent application WO/2017/144877. C.S. acknowledges grant support from AstraZeneca, Boehringer-Ingelheim, Bristol Myers Squibb, Pfizer, Roche-Ventana, Invitae (previously Archer Dx, Inc., collaboration in minimal residual disease sequencing technologies), Ono Pharmaceutical, and Personalis. He is an AstraZeneca advisory board member, chief investigator for the AZ MeRmaiD 1 and 2 clinical trials, co-chief investigator of the NHS Galleri trial funded by GRAIL, and a paid member of GRAIL’s SAB. He receives consultant fees from Achilles Therapeutics (also a SAB member), Bicycle Therapeutics (also a SAB member), Genentech, Medicxi, China Innovation Center of Roche (CICoR), formerly the Roche Innovation Center – Shanghai, Metabomed (until July 2022), and the Sarah Cannon Research Institute. C.S. has received honoraria from Amgen, AstraZeneca, Pfizer, Novartis, GlaxoSmithKline, MSD, Bristol Myers Squibb, Illumina, and Roche-Ventana. C.S. had stock options in Apogen Biotechnologies and GRAIL until June 2021 and currently has stock options in Epic Bioscience and Bicycle Therapeutics and has stock options and is co-founder of Achilles Therapeutics., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease., (© 2023. The Author(s), under exclusive licence to ADMC Associazione Differenziamento e Morte Cellulare.)

Artificial sweeteners are used as calorie-free sugar substitutes in many food products and their consumption has increased substantially over the past years 1 . Although generally regarded as safe, some concerns have been raised about the long-term safety of the consumption of certain sweeteners 2-5 . In this study, we show that the intake of high doses of sucralose in mice results in immunomodulatory effects by limiting T cell proliferation and T cell differentiation. Mechanistically, sucralose affects the membrane order of T cells, accompanied by a reduced efficiency of T cell receptor signalling and intracellular calcium mobilization. Mice given sucralose show decreased CD8 + T cell antigen-specific responses in subcutaneous cancer models and bacterial infection models, and reduced T cell function in models of T cell-mediated autoimmunity. Overall, these findings suggest that a high intake of sucralose can dampen T cell-mediated responses, an effect that could be used in therapy to mitigate T cell-dependent autoimmune disorders., (© 2023. The Author(s).)

The synthesis of serine from glucose is a key metabolic pathway supporting cellular proliferation in healthy and malignant cells. Despite this, the role that this aspect of metabolism plays in germinal center biology and pathology is not known. Here, we performed a comprehensive characterization of the role of the serine synthesis pathway in germinal center B cells and lymphomas derived from these cells. We demonstrate that upregulation of a functional serine synthesis pathway is a metabolic hallmark of B cell activation and the germinal center reaction. Inhibition of phosphoglycerate dehydrogenase (PHGDH), the first and rate-limiting enzyme in this pathway, led to defective germinal formation and impaired high-affinity antibody production. In addition, overexpression of enzymes involved in serine synthesis was a characteristic of germinal center B cell-derived lymphomas, with high levels of expression being predictive of reduced overall survival in diffuse large B cell lymphoma. Inhibition of PHGDH induced apoptosis in lymphoma cells, reducing disease progression. These findings establish PHGDH as a critical player in humoral immunity and a clinically relevant target in lymphoma.

Eukaryotic cells have developed complex systems to regulate the production and response to reactive oxygen species (ROS). Different ROS control diverse aspects of cell behaviour from signalling to death, and deregulation of ROS production and ROS limitation pathways are common features of cancer cells. ROS also function to modulate the tumour environment, affecting the various stromal cells that provide metabolic support, a blood supply and immune responses to the tumour. Although it is clear that ROS play important roles during tumorigenesis, it has been difficult to reliably predict the effect of ROS modulating therapies. We now understand that the responses to ROS are highly complex and dependent on multiple factors, including the types, levels, localization and persistence of ROS, as well as the origin, environment and stage of the tumours themselves. This increasing understanding of the complexity of ROS in malignancies will be key to unlocking the potential of ROS-targeting therapies for cancer treatment., (© 2022. Springer Nature Limited.)

The p53 transcription factor coordinates wide-ranging responses to stress that contribute to its function as a tumour suppressor. The responses to p53 induction are complex and range from mediating the elimination of stressed or damaged cells to promoting survival and repair. These activities of p53 can modulate tumour development but may also play a role in pathological responses to stress such as tissue damage and repair. Using a p53 reporter mouse, we have previously detected strong induction of p53 activity in the liver of mice treated with the hepatotoxin carbon tetrachloride (CCl 4 ). Here, we show that p53 functions to support repair and recovery from CCl 4 -mediated liver damage, control reactive oxygen species (ROS) and limit the development of hepatocellular carcinoma (HCC), in part through the activation of a detoxification cytochrome P450, CYP2A5 (CYP2A6 in humans). Our work demonstrates an important role for p53-mediated redox control in facilitating the hepatic regenerative response after damage and identifies CYP2A5/CYP2A6 as a mediator of this pathway with potential prognostic utility in human HCC., (© 2021. The Author(s).)

Genetically encoded probes are widely used to visualize cellular processes in vitro and in vivo. Although effective in cultured cells, fluorescent protein tags and reporters are suboptimal in vivo because of poor tissue penetration and high background signal. Luciferase reporters offer improved signal-to-noise ratios but require injections of luciferin that can lead to variable responses and that limit the number and timing of data points that can be gathered. Such issues in studying the critical transcription factor p53 have limited insight on its activity in vivo during development and tissue injury responses. Here, by linking the expression of the near-infrared fluorescent protein iRFP713 to a synthetic p53-responsive promoter, we generated a knock-in reporter mouse that enabled noninvasive, longitudinal analysis of p53 activity in vivo in response to various stimuli. In the developing embryo, this model revealed the timing and localization of p53 activation. In adult mice, the model monitored p53 activation in response to irradiation and paracetamol- or CCl 4 -induced liver regeneration. After irradiation, we observed potent and sustained activation of p53 in the liver, which limited the production of reactive oxygen species (ROS) and promoted DNA damage resolution. We propose that this new reporter may be used to further advance our understanding of various physiological and pathophysiological p53 responses.

Competing Interests: The authors declare no competing interest.

Serine is a non-essential amino acid that is critical for tumour proliferation and depletion of circulating serine results in reduced tumour growth and increased survival in various cancer models. While many cancer cells cultured in a standard tissue culture medium depend on exogenous serine for optimal growth, here we report that these cells are less sensitive to serine/glycine depletion in medium containing physiological levels of metabolites. The lower requirement for exogenous serine under these culture conditions reflects both increased de novo serine synthesis and the use of hypoxanthine (not present in the standard medium) to support purine synthesis. Limiting serine availability leads to increased uptake of extracellular hypoxanthine, sparing available serine for other pathways such as glutathione synthesis. Taken together these results improve our understanding of serine metabolism in physiologically relevant nutrient conditions and allow us to predict interventions that may enhance the therapeutic response to dietary serine/glycine limitation., (© 2021. The Author(s).)

p53 is an important tumor suppressor, and the complexities of p53 function in regulating cancer cell behaviour are well established. Many cancers lose or express mutant forms of p53, with evidence that the type of alteration affecting p53 may differentially impact cancer development and progression. It is also clear that in addition to cell-autonomous functions, p53 status also affects the way cancer cells interact with each other. In this review, we briefly examine the impact of different p53 mutations and focus on how heterogeneity of p53 status can affect relationships between cells within a tumor., (© 2021 Pilley et al.; Published by Cold Spring Harbor Laboratory Press.)

Fructose intake has increased substantially throughout the developed world and is associated with obesity, type 2 diabetes and non-alcoholic fatty liver disease. Currently, our understanding of the metabolic and mechanistic implications for immune cells, such as monocytes and macrophages, exposed to elevated levels of dietary fructose is limited. Here, we show that fructose reprograms cellular metabolic pathways to favour glutaminolysis and oxidative metabolism, which are required to support increased inflammatory cytokine production in both LPS-treated human monocytes and mouse macrophages. A fructose-dependent increase in mTORC1 activity drives translation of pro-inflammatory cytokines in response to LPS. LPS-stimulated monocytes treated with fructose rely heavily on oxidative metabolism and have reduced flexibility in response to both glycolytic and mitochondrial inhibition, suggesting glycolysis and oxidative metabolism are inextricably coupled in these cells. The physiological implications of fructose exposure are demonstrated in a model of LPS-induced systemic inflammation, with mice exposed to fructose having increased levels of circulating IL-1β after LPS challenge. Taken together, our work underpins a pro-inflammatory role for dietary fructose in LPS-stimulated mononuclear phagocytes which occurs at the expense of metabolic flexibility.

Many tumour cells show dependence on exogenous serine and dietary serine and glycine starvation can inhibit the growth of these cancers and extend survival in mice. However, numerous mechanisms promote resistance to this therapeutic approach, including enhanced expression of the de novo serine synthesis pathway (SSP) enzymes or activation of oncogenes that drive enhanced serine synthesis. Here we show that inhibition of PHGDH, the first step in the SSP, cooperates with serine and glycine depletion to inhibit one-carbon metabolism and cancer growth. In vitro, inhibition of PHGDH combined with serine starvation leads to a defect in global protein synthesis, which blocks the activation of an ATF-4 response and more broadly impacts the protective stress response to amino acid depletion. In vivo, the combination of diet and inhibitor shows therapeutic efficacy against tumours that are resistant to diet or drug alone, with evidence of reduced one-carbon availability. However, the defect in ATF4-response seen in vitro following complete depletion of available serine is not seen in mice, where dietary serine and glycine depletion and treatment with the PHGDH inhibitor lower but do not eliminate serine. Our results indicate that inhibition of PHGDH will augment the therapeutic efficacy of a serine depleted diet.

The p53 tumor suppressor protein is a potent activator of proliferative arrest and cell death. In normal cells, this pathway is restrained by p53 protein degradation mediated by the E3-ubiquitin ligase activity of MDM2. Oncogenic stress releases p53 from MDM2 control, so activating the p53 response. However, many tumors that retain wild-type p53 inappropriately maintain the MDM2-p53 regulatory loop in order to continuously suppress p53 activity. We have shown previously that single point mutations in the human MDM2 RING finger domain prevent the interaction of MDM2 with the E2/ubiquitin complex, resulting in the loss of MDM2's E3 activity without preventing p53 binding. Here, we show that an analogous mouse MDM2 mutant (MDM2 I438K) restrains p53 sufficiently for normal growth but exhibits an enhanced stress response in vitro. In vivo , constitutive expression of MDM2 I438K leads to embryonic lethality that is rescued by p53 deletion, suggesting MDM2 I438K is not able to adequately control p53 function through development. However, the switch to I438K expression is tolerated in adult mice, sparing normal cells but allowing for an enhanced p53 response to DNA damage. Viewed as a proof of principle model for therapeutic development, our findings support an approach that would inhibit MDM2 E3 activity without preventing MDM2/p53 binding as a promising avenue for development of compounds to activate p53 in tumors with reduced on-target toxicities., (© 2021 Humpton et al.; Published by Cold Spring Harbor Laboratory Press.)

The concept that dietary changes could improve the response to cancer therapy is extremely attractive to many patients, who are highly motivated to take control of at least some aspect of their treatment. Growing insight into cancer metabolism is highlighting the importance of nutrient supply to tumor development and therapeutic response. Cancers show diverse metabolic requirements, influenced by factors such as tissue of origin, microenvironment, and genetics. Dietary modulation will therefore need to be matched to the specific characteristics of both cancers and treatment, a precision approach requiring a detailed understanding of the mechanisms that determine the metabolic vulnerabilities of each cancer., Competing Interests: Declaration of Interests K.H.V. is on the Board of Directors and shareholder of Bristol Myers Squibb, a shareholder of GRAIL Inc, and on the Science Advisory Board (with stock options) of PMV Pharma, RAZE Therapeutics, and Volastra Therapeutics. She is also on the Scientific Advisory Board of Ludwig Cancer. K.H.V. is a co-founder and consultant of Faeth Therapeutics, funded by Khosla Ventures. She has been in receipt of research funding from Astex Pharmaceuticals and AstraZeneca and contributed to CRUK Cancer Research Technology filing of patent application WO/2017/144877., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Phosphorylation of MDM2 by ATM upon DNA damage is an important mechanism for deregulating MDM2, thereby leading to p53 activation. ATM phosphorylates multiple residues near the RING domain of MDM2, but the underlying molecular basis for deregulation remains elusive. Here we show that Ser429 phosphorylation selectively enhances the ubiquitin ligase activity of MDM2 homodimer but not MDM2-MDMX heterodimer. A crystal structure of phospho-Ser429 (pS429)-MDM2 bound to E2-ubiquitin reveals a unique 3 10 -helical feature present in MDM2 homodimer that allows pS429 to stabilize the closed E2-ubiquitin conformation and thereby enhancing ubiquitin transfer. In cells Ser429 phosphorylation increases MDM2 autoubiquitination and degradation upon DNA damage, whereas S429A substitution protects MDM2 from auto-degradation. Our results demonstrate that Ser429 phosphorylation serves as a switch to boost the activity of MDM2 homodimer and promote its self-destruction to enable rapid p53 stabilization and resolve a long-standing controversy surrounding MDM2 auto-degradation in response to DNA damage.

The importance of cancer-cell-autonomous functions of the tumour suppressor p53 (encoded by TP53 ) has been established in many studies, but it is now clear that the p53 status of the cancer cell also has a profound impact on the immune response. Loss or mutation of p53 in cancers can affect the recruitment and activity of myeloid and T cells, allowing immune evasion and promoting cancer progression. p53 can also function in immune cells, resulting in various outcomes that can impede or support tumour development. Understanding the role of p53 in tumour and immune cells will help in the development of therapeutic approaches that can harness the differential p53 status of cancers compared with most normal tissue., Competing Interests: Competing interestsK.H.V. is on the Board of Directors and shareholder of Bristol Myers Squibb, a shareholder of GRAIL, Inc. and on the Science Advisory Board of PMV Pharma, RAZE Therapeutics, Volestra Therapeutics and Ludwig Cancer. She is a co-founder and consultant of Faeth Therapeutics, funded by Khosla Ventures. She has been in receipt of research funding from Astex Pharmaceuticals and AstraZeneca and contributed to CRUK Cancer Research Technology filing of Patent Application WO/2017/144877., (© 2020. Published by The Company of Biologists Ltd.)

The TIGAR protein has antioxidant activity that supports intestinal tissue repair and adenoma development. Using a pancreatic ductal adenocarcinoma (PDAC) model, we show that reactive oxygen species (ROS) regulation by TIGAR supports premalignant tumor initiation while restricting metastasis. Increased ROS in PDAC cells drives a phenotypic switch that increases migration, invasion, and metastatic capacity. This switch is dependent on increased activation of MAPK signaling and can be reverted by antioxidant treatment. In mouse and human, TIGAR expression is modulated during PDAC development, with higher TIGAR levels in premalignant lesions and lower TIGAR levels in metastasizing tumors. Our study indicates that temporal, dynamic control of ROS underpins full malignant progression and helps to rationalize conflicting reports of pro- and anti-tumor effects of antioxidant treatment., Competing Interests: Declaration of Interests K.H.V. is on the board of directors and a shareholder of Bristol Myers Squibb, a shareholder of GRAIL, Inc., and on the science advisory board of PMV Pharma, RAZE Therapeutics, Volestra Therapeutics,Inc and Ludwig Cancer. She is a co-founder and consultant of Faeth Therapeutics, funded by Khosla Ventures. She has been in receipt of research funding from Astex Pharmaceuticals and AstraZeneca and contributed to CRUK Cancer Research Technology filing of Patent Application WO/2017/144877. D.A.T. serves on the scientific advisory board and holds shares in Leap Therapeutics and Surface Oncology. D.A.T. serves on the SAB of Cygnal Therapeutics. D.A.T. has research support from ONO Therapeutics, FibroGen, and Halozyme., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Loss of p53 function contributes to the development of many cancers. While cell-autonomous consequences of p53 mutation have been studied extensively, the role of p53 in regulating the anti-tumor immune response is still poorly understood. Here, we show that loss of p53 in cancer cells modulates the tumor-immune landscape to circumvent immune destruction. Deletion of p53 promotes the recruitment and instruction of suppressive myeloid CD11b + cells, in part through increased expression of CXCR3/CCR2-associated chemokines and macrophage colony-stimulating factor (M-CSF), and attenuates the CD4 + T helper 1 (Th1) and CD8 + T cell responses in vivo. p53-null tumors also show an accumulation of suppressive regulatory T (Treg) cells. Finally, we show that two key drivers of tumorigenesis, activation of KRAS and deletion of p53, cooperate to promote immune tolerance., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Cancer metastasis depends on cell survival following loss of extracellular matrix attachment and dissemination through the circulation. The metastatic spread can be enhanced by the clustering of detached cancer cells and increased antioxidant defense. Here, we link these responses by describing how cell clustering limits reactive oxygen species (ROS). Loss of attachment causes mitochondrial perturbations and increased ROS production. The formation of cell clusters induces a hypoxic environment that drives hypoxia-inducible factor 1-alpha (Hif1α)-mediated mitophagy, clearing damaged mitochondria and limiting ROS. However, hypoxia and reduced mitochondrial capacity promote dependence on glycolysis for ATP production that is supported by cytosolic reductive metabolism. Preventing this metabolic adaptation or disruption of cell clusters results in ROS accumulation, cell death, and a reduction of metastatic capacity in vivo. Our results provide a mechanistic explanation for the role of cell clustering in supporting survival during extracellular matrix detachment and metastatic spread and may point to targetable vulnerabilities., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Activating KRAS mutations are found in nearly all cases of pancreatic ductal adenocarcinoma (PDAC), yet effective clinical targeting of oncogenic KRAS remains elusive. Understanding of KRAS-dependent PDAC-promoting pathways could lead to the identification of vulnerabilities and the development of new treatments. We show that oncogenic KRAS induces BNIP3L /NIX expression and a selective mitophagy program that restricts glucose flux to the mitochondria and enhances redox capacity. Loss of Nix restores functional mitochondria to cells, increasing demands for NADPH reducing power and decreasing proliferation in glucose-limited conditions. Nix deletion markedly delays progression of pancreatic cancer and improves survival in a murine (KPC) model of PDAC. Although conditional Nix ablation in vivo initially results in the accumulation of mitochondria, mitochondrial content eventually normalizes via increased mitochondrial clearance programs, and pancreatic intraepithelial neoplasia (PanIN) lesions progress to PDAC. We identify the KRAS-NIX mitophagy program as a novel driver of glycolysis, redox robustness, and disease progression in PDAC. SIGNIFICANCE: NIX-mediated mitophagy is a new oncogenic KRAS effector pathway that suppresses functional mitochondrial content to stimulate cell proliferation and augment redox homeostasis. This pathway promotes the progression of PanIN to PDAC and represents a new dependency in pancreatic cancer. This article is highlighted in the In This Issue feature, p. 1143 ., (©2019 American Association for Cancer Research.)

Heavy isotope labeled metabolites are readily detected by mass spectrometry and are commonly used to analyze the rates of metabolic reactions in cultured cells. The ability to detect labeled metabolites-and infer fluxes-is influenced by a number of factors that can confound simplistic comparative assays. The accumulation of labeled metabolites is strongly influenced by the pool size of the metabolite of interest and also by changes in downstream reactions, which are not always fully perceived. Here, we describe a method that overcomes some of these limitations and allows simple calculation of reaction rates under low nutrient, rapid reaction rate conditions. Acutely increasing the pool of the metabolite of interest (by adding a pulse of excess unlabeled nutrient to the cells) rapidly increases accumulation of labeled metabolite, facilitating a more accurate assessment of reaction rate.

Tracing the fate of carbon-13 ( 13 C) labeled metabolites within cells by liquid chromatography mass spectrometry (LCMS) is a powerful analytical technique used for many years in the study of cell metabolism. Conventional experiments using LCMS and labeled nutrients tend to track the incorporation of 13 C from exogenous nutrients (such as amino acids) into other, relatively proximal, cellular metabolites. Several labs have extended this technique to track transfer of 13 C from the metabolite pool onto macromolecules, such as DNA, where methylation acts as an important functional modification. Here we describe a complete method that integrates previously established techniques to simultaneously track the use of 13 C-serine or 13 C-methionine into metabolite pools of the methionine cycle and into methylation of DNA and RNA. Given the ability to track methyl-transfer in a time-dependent way, this technique can provide temporal information about active methyl-transfer as well as quantification of total DNA/RNA methylation levels.

Background: In response to oncogenic stress, the tumour suppressor protein p53 can induce the elimination of cells through induction of cell death or senescence, helping to restrain malignant progression. Conversely, under nutrient stress, p53 can protect cells by supporting metabolic adaptation. Many cancers express mutant p53 proteins that have lost the cell-elimination properties of wild-type p53. However, a previous report showed that a tumour-derived mutant can retain the ability to support cells under glutamine starvation., Results: We show that a commonly occurring p53 mutant, R248W, retains wild-type ability to support survival under serine starvation. R248W, but not R175H, can engage p21 and MDM2, which both function to limit oxidative stress and facilitate the switch to de novo serine synthesis. In vivo, the growth of R248W-expressing tumours is resistant to dietary depletion of serine and glycine, correlating with an increased capacity to limit ROS compared to tumours expressing R175H. Human cancers expressing this p53 mutant show a worse outcome., Conclusion: Our work shows that mutant p53s can selectively retain wild-type p53 functions that allow adaptation to serine starvation through the activation of antioxidant defence pathways. Tumours containing this p53 mutation are resistant to serine-limited conditions and less responsive to therapy., Competing Interests: Not applicableNot applicableKV is on the Board of Directors and shareholder of Bristol Myers Squib, on the Advisory Board and shareholder of Grail Inc., and on the advisory board of PMV Pharma and RAZE therapeutics. ODKM and KHV are inventors on CRUK Patent Application WO/2017/144877.Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Numerous mechanisms to support cells under conditions of transient nutrient starvation have been described. Several functions of the tumor-suppressor protein p53 can contribute to the adaptation of cells to metabolic stress and help cancer cell survival under nutrient-limiting conditions. We show here that p53 promotes the expression of SLC1A3, an aspartate/glutamate transporter that allows the utilization of aspartate to support cells in the absence of extracellular glutamine. Under glutamine deprivation, SLC1A3 expression maintains electron transport chain and tricarboxylic acid cycle activity, promoting de novo glutamate, glutamine, and nucleotide synthesis to rescue cell viability. Tumor cells with high levels of SLC1A3 expression are resistant to glutamine starvation, and SLC1A3 depletion retards the growth of these cells in vitro and in vivo, suggesting a therapeutic potential for SLC1A3 inhibition., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)